The one rule to remember
EPDM (ethylene propylene diene monomer) is excellent with water, steam, glycol brake fluid and many polar chemicals, and it has outstanding weather and ozone resistance. But it swells badly in petroleum products. Never use EPDM with mineral oil, hydraulic oil, fuel or grease. That single incompatibility is the most common EPDM mistake and the fastest way to a failed seal.
Where EPDM excels
- Hot water and steam. EPDM is the standard elastomer for water and steam service, where FKM and NBR both struggle.
- Brake fluid. Glycol-based (DOT 3/4/5.1) brake fluid attacks NBR and FKM but suits EPDM.
- Weather, ozone and UV. EPDM resists outdoor ageing far better than nitrile, so it is common in exterior and roofing seals.
- Polar fluids and many chemicals. Ketones, alcohols, dilute acids and bases, and phosphate-ester hydraulic fluids are generally compatible.
- Cold. Good low-temperature flexibility, typically to around −50 °C.
Where EPDM fails
- Petroleum oil, fuel and grease. Severe swelling — the classic misuse.
- Mineral-oil hydraulic systems. Same problem; use NBR or FKM instead.
- Aromatic and chlorinated solvents. Generally poor.
| Medium | EPDM | Better alternative if EPDM fails |
|---|---|---|
| Hot water / steam | Excellent | — |
| Glycol brake fluid | Excellent | — |
| Ozone / weather / UV | Excellent | — |
| Mineral / hydraulic oil | Poor (swells) | NBR or FKM |
| Petrol / diesel fuel | Poor (swells) | NBR (fuel grade) or FKM |
| Aromatic solvents | Poor | FKM |
Temperature range
Sulphur-cured EPDM typically runs from about −50 °C to +120 °C; peroxide-cured grades reach higher, roughly +150 °C, with better compression-set resistance. As always, temperature and media must be satisfied together — a compatible fluid at too high a temperature still fails.
Choosing between EPDM, NBR and FKM
The three cover most industrial sealing between them:
- Water, steam, brake fluid, outdoor → EPDM.
- Petroleum oil, hydraulic, most fuel near ambient → NBR.
- Hot oil, fuel, aggressive chemicals → FKM.
Get the media split right first, then size the ring for the correct squeeze and gland fill. The material page for EPDM lists its temperature band and Parker compound letters.
Frequently asked questions
Can EPDM be used with oil? No. EPDM swells badly in petroleum oils, fuels and greases. Use NBR or FKM for oil, and reserve EPDM for water, steam, brake fluid and weathering duty.
Is EPDM good for steam? Yes. EPDM is one of the standard choices for hot water and steam, where nitrile and fluoroelastomer both perform poorly.
Does EPDM work with brake fluid? Glycol-based (DOT 3/4/5.1) brake fluid, yes. This is a signature EPDM application, unlike silicone DOT 5, which is a different chemistry.